564: Mini Moons Astronomy Cast 564: Mini Moons by Fraser Cain & Dr. Pamela Gay Last month astronomers announced that they had detected a tiny asteroid that had been captured by the Earth's gravity well and had been sharing our orbit for a few years. Today, let's talk about the smallest moons in the Solar System.Last month astronomers announced that they had detected a tiny asteroid that had been captured by the Earth's gravity well and had been sharing our orbit for a few years. Today, let's talk about the smallest moons in the Solar System.